MOM protecting group

Decyl-5-methoxy-l-naphthol [Reduction of a Secondary Benzylic Alcohol to a Methylene Group with Concomitant Loss of a MOM Protecting Group].167... 

A straightforward synthesis (Scheme 3) of a furocoumarin-thymidine furan-side adduct was developed <1997JOC2630>. The methoxymethyl (MOM)-protecting group in 33 was removed in 91% yield with ethanolic HCl, and the resulting phenol 34 was condensed with dimethylacetamide dimethyl acetal in the presence of 4 A... 

Treatment with aqueous sulfuric acid cleaves the MOM protective group (which consists of an acetal structure) to give compound 48. 

A methoxymethyl [MOM] protecting group at C-2 could not be removed following esterification ... 

A methoxymethyl (MOM) protecting group at N-3 was chosen based on its successful use in the total synthesis of nucleoside Q.31 Our previous experience with the total synthesis of rigidin vide supra) suggested BOM protection for the N-1 position and a 2,4-dimethoxybenzyl (DMB)... 

Similar conditions for the formation of a (Z)-configured ketone enolate (6) at low temperature were applied by Myles and coworkers in their total synthesis of (-l-)-discoder-molide (10, equation 3f. Deprotonation of the ethyl ketone 7 with LiHMDS as base at —78 °C and addition of TMEDA delivered a (Z)-configured enolate (8), which was subsequently alkylated with allyl iodide 9. Thereby, chelation of the lithium enolate with the adjacent MOM protecting group led to a conformationally stable chair-like transition-state 8, in which the attack of the alkylation reagent 9 (represented in 8 by E+) could only occur from the site opposite to the bulky group R. Thus, the alkylation prodnct 10 was obtained with a good diastereomeric selectivity at C of 83-85% ds. 

Reaction of the monocyanoethyl-protected TTF 738 with cesium hydroxide in a mixture of methanol and DMF led to the deprotected thiolate, which was further alkylated with the bromobutyl-substituted MOM-triptycene 739 to give the MOM-TTF 740 in 89% yield (MOM = methoxymethyl). The MOM protecting group was removed quantitatively under acidic conditions and the resulting hydroquinone was oxidized to yield the TTF-quinone 741 in 54% yield (Scheme 109). The preparation of the pyrrolo-TTF derivatives 25 was accomplished in a similar way <1998JOC1198>. 

The first synthesis of the hexacyclic himandrine skeleton was achieved by L.N. Mander and co-workers. The last six-membered heterocycle was formed via an intramolecular Wacker-type oxidation in which the terminal alkene side-chain reacted with the secondary amine functionality. The oxidation was conducted in anhydrous acetonitrile to insure that the Pd-alkene complex was substituted exclusively by the internal nucleophile. The resulting six-membered enamine was then hydrogenated and the MOM protecting groups removed to give the desired final product. 

Obtained by exposure of the carboxylic acid derived from the Claisen rearrangement to the esterification conditions (OH, OH,SOCl,), resulting in loss of the MOM protecting group. 

Easily prepared and removed under mild acidic conditions, the methoxymethyl ether (MOM) protecting group has been widely utilized with a variety of tartrate derivatives. Treatment of diethyl tartrate (lb) with excess chloromethyl methyl ether in the presence of 7V, -diiso-propylethylamine furnishes in 79% yield diethyl 2,3-0-bis(methoxymethyl)-L-tartrate (623). This reaction is easily performed on a scale greater than 100 g [199,200]. 

Ruhland reported a novel solid-phase C2-lithiation of the indole ring [279] using a linker that resembled the MOM-protecting group (Scheme 16). Lithiation of resin-bound indole 73 was accomplished by treatment with tert-butyllithium in toluene followed by quenching with benzonitrile. Reductive cleavage of 74 then gave amine 75 in an overall yield of 2%, proof of principle that this type of transformation is possible. 

Reductive cycHzations have been shown to be diastereoselective in the synthesis of bicyclic products as well as various macrocycles. There are also instances of chirahty transfer in intermolecular reductive couphngs. The synthesis of anti-1,2-diols has been demonstrated using a-alkoxyaldehydes with a methoxymethyl ether (MOM) protecting group and mono-aryl internal alkynes (Scheme 8.25) [49]. Dias-tereoselectivities are high for the formation of anfi-l,2-diols in cases where the aldehyde has a branched sp -P-carbon. 

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